The Boston Globe
Brigham and Women’sHospital. David L. Ryan/The Boston Globe
The infectious disease clinician who worked closely with the cardiac surgery department had a feeling something was wrong. It was 2018, and she mentioned to colleagues at Brigham and Women’s Hospital the unusual appearance of a suspicious bacteria, which had appeared several times over the past year and a half. The rare bacterium, Mycobacterium abscessus, can sometimes cause nosocomial infections, often from contaminated water. But the number of times hospital patients had tested positive for it struck him as unusual.
What followed was a deep dive into infection control that ultimately identified four patients who had been infected with the same strain of M abscessus. Despite efforts to treat the infections, three of the four patients died.
Eventually, the hospital discovered the culprit: a water purification system powering an ice and water machine on the heart unit.
The analysis of where the bacteria originated and the lessons that followed for the hospital in infection control were highlighted in a study published by Brigham clinicians Monday in the Annals of Internal Medicine. The article describes the detective work involved in finding a potentially deadly pathogen and shares key information about hospital protocols that the researchers hope other facilities will take to heart.
“Every health care facility in the world will have a potential (encounter) with nosocomial infections,” said Dr. Michael Klompas, infectious disease physician and hospital Brigham and Women’s epidemiologist, who conducted the investigation. “It’s not a unique problem for us. If we pretend it doesn’t exist, we will never be as successful as possible if we face them head-on.
Infectious disease expert Dr Todd Ellerin applauded what he described as a complex epidemiological investigation, saying it was unusual for a system to find the source of such outbreaks.
“There are a lot of detectives out there,” said Ellerin, acting chief of medicine and chief of infectious diseases at South Shore Health. Ellerin was not part of the investigation, although South Shore is clinically affiliated with the Brigham in several specialties. “The Brigham had to be like Sherlock Holmes.”
Massachusetts hospitals have faced several waterborne bacterial pathogens in recent years. In 2020, Brigham and Women’s saw a number of infections and three patient deaths from the bacterium Burkholderia cepacia, after patients were contaminated with a type of life support known as extracorporeal membrane oxygenation , which oxygenates a person’s blood outside their body. In December, the Franciscan Children’s Hospital had 36 children testing positive for the same bacteria; officials suspected it came from tap water.
Abscessus is rare for hospitals, with outbreaks often associated with water systems such as heating-cooling devices used for patients undergoing heart bypass surgery and hospital plumbing systems. Although generally of little threat to healthy people, infections can be problematic for vulnerable patients and require large amounts of antibiotics to treat, Ellerin said.
In June 2018, Brigham’s infection control department was alerted to three heart surgery patients who developed an invasive infection from the bacteria. Two of the patients had surgically implanted heart pumps called left ventricular assist devices. Another was a heart surgery patient who was immunocompromised.
Klompas said one of the first challenges was recognizing that something was even happening, given the small number of cases with several months apart.
“We regularly receive these alerts from various clinicians, and we often investigate and find nothing,” Klompas said. “But that, we looked at, and said it was unusual, and dived deeper.”
But were there other patients? The hospital has searched its own microbiology database since 2015, looking for patients in the hospital during a given period who had a culture that tested positive for the bacteria. This search uncovered a fourth infected patient, also with a left ventricular assist device.
The key question: Was there a central source inside the hospital? The four men, aged over 50, had been admitted to the cardiac surgery intensive care unit and a descent unit, located on a single floor of the hospital, each very ill and hospitalized for a period of weeks to months.
It was not immediately clear what else the patients had in common. Three of the four underwent surgery at the Brigham, but all in different operating rooms with different machines, and the infection had manifested itself weeks after their heart surgery. The patients had occupied several widely different rooms. Three of the four had been intubated for long periods. However, for two of these patients, months passed between when they were on a ventilator and when the bacteria appeared, leading officials to conclude that the ventilators were probably not the source. collective.
But the bacterium carries a genetic fingerprint, which would tell the hospital whether the patients had been infected with the same strain – and from the same source. Doing such sequencing required the help of a research lab at the Harvard School of Public Health, which has the capabilities to perform tests on such an unusual bacterium.
Most strains are unrelated and the research stops there. But in this case, the genetic strains matched almost perfectly.
The hospital took cultures from the sinks and showers in each of the rooms occupied by the patients, but the levels of mycobacteria were non-existent or too low, which excludes it as a probable source. But experts found high levels of mycobacteria in samples from ice and water machines in the cardiac surgery intensive care unit and the descent unit. DNA extracted from the machine’s samples exactly matched a gene in the patient outbreak.
Records showed that the machines had been cleaned and maintained properly. But further tests revealed that chlorine levels In the problem units were undetectable, due to a commercial water purification system the hospital had installed in the plumbing lines leading to these units. The filter included a carbon filter and an ultraviolet irradiation unit, both of which lower chlorine concentrations. The system was designed to improves the taste, odor and purity of water, but allows bacteria, normally killed by chlorine, to grow.
“You wouldn’t be surprised if other hospitals and health systems have similar water systems in place, installed with the best of intentions,” Klompas said. “You would think that putting a filter would make the water better. Weak and behold, it has unintended consequences. That was the reason for posting.
According to the study, mycobacteria likely come from municipal water, which often contains low levels of bacteria. Experts suspect that infected patients may have been particularly prone to infection, given their long length of stay. Nurses noted that these particular patients were consuming large amounts of ice.
Beyond removing problematic ice and water machines and the purification system, the hospital changed how and how often it cleans and maintains its ice and water machines.
The hospital also now uses sterile, distilled or filtered water for drinking and caring for the most vulnerable patients.
Tap water “is good for you and me and anyone who is healthy. Our immune system can take care of it. But if you’re vulnerable, you might not be able to do it,” Klompas said.
Ellerin, of South Shore Health, said there are lessons for other health systems to learn about the need for more comprehensive hospital monitoring of its water systems. The study is also a critical reminder of the importance of reducing the exposure of a hospital’s most vulnerable patients to tap water.
No further cases of hospital-associated abscess M have occurred through September 2022.
Klompas said the outbreak is a warning sign that national standards for monitoring water inside a hospital — typically focused on Legionnaires’ infections — might not be stringent enough.
“It turns out that things good enough to get rid of Legionella might not be good enough to get rid of mycobacteria,” Klompas said. “This is another (area of interest) for federal regulars…to reduce the risk of mycobacteria.”